/Engine/Source/Editor/UnrealEd/Public/FileHelpers.h
Returns true if the specified map filename is valid for loading or saving. When returning false, OutErrorMessage is supplied with a display string describing the reason why the map name is invalid.
static bool IsValidMapFilename ( const [FString](API\Runtime\Core\Containers\FString) & MapFilename, [FText](API\Runtime\Core\Internationalization\FText) & OutErrorMessage )